The legend of the mysterious mermaids and deep-sea tribes has always been the favorite after-dinner story of the villagers in Happy Village. Until one day, Tantan Cat accidentally encountered a mermaid princess who escaped from the bottom of the sea and came ashore, and this legend became a reality. Tantan Cat and his friends rescued the mermaid princess, but soon the evil deep-sea tribe followed closely. The princess hid important clues, which were the key to finding the powerful magic stone. Tantan Cat and his friends had to face the deep-sea witch with powerful black magic, and Dr. Oolong, Tantan Cat's mortal enemy who was seduced by magic. Whoever finds the magic stone first will have an absolute advantage. On this rugged road of exploration, the strongman Tantan Cat must find his own true "power" to help the mermaid princess find the strongest magic to defeat the deep-sea tribe. Everyone placed their hopes on this extraordinary adventure to ensure the safety between the sea and the land.